Cardiac arrhythmias occur in as many as 62% of anesthetized patients. They interfere with myocardial performance and impair myocardial oxygenation in patients with coronary artery disease. It is generally held that anesthetic-include changes in pacemaker function are responsible for arrhythmias. With the widespread utilization of cardiac electrophysiologic techniques for the study of non-anesthetic caused arrhythmias, the role of altered conduction and refractoriness in their genesis has become appreciated. Information gained from electrophysiologic studies has been effectively applied in the management of clinical rhythm disturbances. Comparable studies for anesthetic-related arrhythmias do not exist. Only recently have cardiac electrophysiologic investigations of anesthetic effects on dogs have been undertaken utilizing catheter His bundle recording and atrial extrastimulation techniques. Since the catheter technique does not permit measurements in the awake (control) state in dogs, we have developed electrodes suitable for long-term implantation and control electrophysiologic measurements in dogs. We propose to perform awake-to-anesthetized state and dose-response cardiac electrophysiologic comparisons for several potent volatile inhalation agents utilizing dogs with chronically implanted electrodes. We will also evaluate the electrophysiologic actions of several commonly used intravenous laboratory anesthetics, drugs which have previously been used for anesthesia in dogs used for cardiac electrophysiologic investigations of anti-arrhythmic and other drug effects. We expect our findings to enable the anesthesiologist to more effectively manage clinical cardiac rhythm and conduction disturbances.